Trigger mechanism for automatic firearms



Oct. 9, 1956 E. HEPPERLE ETAL 2,765,709

TRIGGER MECHANISM FDR AUTOMATIC FIREARMS 3 Sheets-Sheet 1 Filed May 27, 1950 INVENTO as E. HEPPERLE ETAL 2,765,709

TRIGGER MECPANISM FOR AUTOMATIC FIREARMS Oct. 9, 1956 5 Sheets-Sheet 2 Filed May 27, 1950 NVENTQRS: Muh/ernann Oct. 9, 1956 E. HEPPERLE ETAL 2,755,709

TRIGGER MECHANISM FOR AUTOMATIC FIREARMS Filed May 27, 1950 3 Sheets-$heet 3 INVENTOfLs E- Hfi b per/e a E/Vu a/emanq Afro ILNEH 2,765,709 Patented Oct. 9, 1956 United States Patent "fiice TRIGGER MECHANISM FOR AUTOMATIC FIREARMS Erwin Hepperle and Ernst Miihlemann, Zurich, Switzerland, assignors to Machine Tool Works Oerlikon, Administration Company, Znrich-Oe'rlikon, Switzerland, a company of Switzerland Application May 27, 1950, Serial No. 164,724 Claims. (Cl. 89-437) The trigger mechanism of automatic firearms must be provided with a device for catching the breech block when firing is interrupted. With such devices it is important that the scar and the catch nose of the breech block impact squarely upon each other. Otherwise if contact is not established over the whole faces of sear and catch nose the edges of the faces will be damaged and may impair the correct operation of the device after some time.

To avoid this danger a known trigger mechanism features a pawl articulated on the scar and rotatable within certain limits which can be actuated by the firing lever and during the forward travel of the breech block also by a cam surface on the breech block. The pawl has faces which in the end positions of the pawls free rotation rest against corresponding faces of the sear whereby on further actuation of the pawl the sear itself is rotated. On releasing the trigger the pawl thereby positively forces the sear into catch position when the breach block starts its forward motion and approaches the sear.

Experience with this device has shown, however, that if the fiiring lever actuating the pawl is released slowly it is possible that the pawl is caught by the breech blocks cam surface in some intermediate position. In this case it may be that the sear will not be rotated fully into catch position.

For the correct operation of this trigger mechanism it is therefore essential that the pawl is released quickly by the firing lever. Since the firing lever usually is acmated by an electromagnet or via a linkage from the mounting this requirement is not always easy to comply with due to the inertia of the actuating means.

The present invention relates to a trigger mechanism which eliminates this disadvantage by providing in the chain of members transmitting the trigger movement to the sear means which on beginning of the release movement of the trigger interrupt this chain immediately in front of the sear, thereby eliminating the effect of the chains inertia and permitting the sear to return to its locking position quickly.

The trigger mechanism can, for instance, be designed in such a way that on one of the intermediate members between the trigger and sear an element is movably arranged which transmits the trigger movement to the next intermediate member and which rests against a spring-actuated movable part disposed in the breech casing in such manner that on actuation of the trigger the element is in positive engagement with the next intermediate member thus permitting operation of the sear whereas as soon as the trigger is released the element is retained by the spring-actuated par-t thereby disconnecting the intermediate member which carries the element from the next intermediate member when the trigger has completed only a small part of its release travel, permitting the spring-actuated sear to return to the locking position independent of the transmitting members in front of the element.

When used in combination with a known trigger release device which is controlled by the feeder of the magazine and efiects catching of the breech block in its rear position when the last round from the magazine has been fired, the trigger mechanism can be designed in such manner that the element which interrupts the chain of intermediate members can be actuated by the spring-actuated part in the breech casing as well as by members which are in engagement with the feeder of the magazine.

The accompanying drawing shows in Figs. 1-12 two constructional examples of the present invention.

Fig. l is a diagrammatic section through a firearm.

Fig. 2 is a section through the trigger mechanism, the breech block being locked by the sear after the trigger release device has been actuated.

Fig. 3 is a section along line IIIIII in Fig. 5 through the members effecting interruption of the trigger chain.

Fig. 4 is a perspective view of the members effecting interruption of the trigger chain.

Fig. 5 is a section along line 'V -V in Fig. 3 through the member effecting interruption of the trigger chain.

Figs. 6-9 are views of the intermediate members of the trigger chain in different positions.

Figs. 1012 are diagrammatic sections through a sec- 0nd example of the present invention in diiferent positions.

According to Fig. l the barrel 1 is connected in known manner to the breech casing 2 which carries the magazine 3. The breech block 4 is slidably arranged in the breech casing 2 and is subjected to the action of the recuperator spring 5. The breech block 4 is fitted with a nose 6 which engages the face 7 of the sear 8. The sear 8 is rotatable about the pin 9 and is subjected to the action of the spring 10 which tends to turn the sear 8 away from its locking position. On the arm opposite the face 7 the sear 8 carries the pawl 11 which is rotatably arranged on the pin 12. The spring 13, disposed in a bore of the sear 8, tends to rotate the sear 8 clockwise. The pawl 11 is arranged in such manner that it can rotate free through a small angle. At the end positions of this free travel the pawl rests against faces of the sear 8. The pawl 11 can be actuated either by the trigger lever 14 which is rotatably arranged on pin 15, or by the cam face 16 of the breech block 4. In normal position, i. e. when the breech block is held by the sear 8 the pawl 11 bears against the top of the breech block thereby preventing the spring 10 from turning the sear 8 out of its locking position. When the pawl 11 is actuated by the trigger lever 14 this support ceases to exist and the sear 8 is rotated thereby releasing the breech block 4. After the trigger has been released the pawl 11 returns to its initial position, thereby protruding into the path of the cam face 16 of the breech block by which it is pressed upwards at the beginning of the breech blocks forward movement. This brings the sear 8 back into locking position and the breech block is caught. This part of the trigger mechanism is already known.

Apart from the trigger lever 14 the pin 15 carries the intermediate lever 17 which is actuated via the pull rod 18 by mechanical or electrical means. 011 the arm 19 of the intermediate lever 17 the pin 21 is arranged on which the pawl 20 and the lever 37 are rotatably disposcd. The pawl 29 is normally held in engagement with the nose 23 of the trigger lever 14 by the torsional spring 22. As shown in Figs. 3 and 4 the lever 37 is fitted with coupling claws 24 engaging with corresponding faces 25 Intermediate of the springs 33, 34 which tend to rotate these parts H in anticlockwise direction.

The stop 26 is arranged in a bore of the breech casing 2. It is acted uponby the spring 27 and can move a certain distance which is limited by the pin 28. If the intermediate lever 17 is in its normal position the pawl 20 does not engage with the stop 26, as shown in Fig. 6. On actuation of the intermediate lever 17 the stop 26 is pressed to the rear by the face 29 of the pawl 20 (Fig. 7) until the latter slides off the front face 30 of the stop 26 whereupon the stop is restored to its initial position by the spring 27. As shown in Fig. 8 the face 31 of the pawl 20 is now situated above the face 32 of the stop 26. Thereby the pawl 20 is still held in engagement with the nose 23 of the trigger lever 14 by the spring 22. If now the intermediate lever 17 is released only by a small amount the pawl 20 is rotated by the face 31 resting on face 32 of the stop 26 and thereby brought out of engagement with the nose 23 of the trigger lever 14 (Fig. 9). This can take place since during the rearward movement of the arm 19, when the trigger is released, the pawl 20 engages the stop 26 and is rotated relatively to the arm 19. This interrupts the connection between intermediate lever 17 and trigger lever 14. The trigger lever 14 is now returned to its initial position by the spring 34 even if the intermediate lever 17 remains in some intermediate position. When the intermediate lever 17 returns to its normal position the pawl 20 is brought again in engagement with the nose 23 of the trigger lever 14 by the spring 22.

In the shown constructional example this mechanism has been combined with a magazine-controlled trigger release device which elfects catching of the breech block after the last round has been fired. As shown in Fig. 2 this device is arranged in a movable casing 46 and contains a plunger 36, subjected to the action of the spring 38 and engaging with the lever 37. The plunger 36 is normally held by the catch 39 of the rocker lever 46. The rocker lever 40 is rotatably mounted on the pin 41 and acted upon by the spring 42. Inside the feeder 43 of the magazine 3 the spring-operated releaser 44 is arranged. When the last round has been removed from the magazine the releaser 44 slides downwards along the oblique face 45 of the magazine and rotates the rocker lever 40 which brings the catch 39 out of engagement with the plunger 36. The latter is moved to the rear by the spring 38 and rotates the lever 37 which, by means of its coupling claws 24, brings the pawl 21) out of engagement with the trigger lever 14. Cocking of the trigger release device is eifected by means of the magazine lock 47 which holds the magazine in place. For removal of the magazine the lock 47 must be moved transversely to. the guns axis whereby the casing 46 is moved to the rear by means of an oblique guide face not shown in the drawing. This movement tensions the spring 38 and permits the catch 39 of the rocker lever 40 which is mounted in the casing 46 to reengage the plunger 36. When a new magazine is placed onto the gun the lock 47 is moved back to its initial position thereby returning the casing 46 to its normal position.

Operation of the device is as follows. On actuation of the trigger the intermediate lever 17 is rotated by the pull rod 18. The pawl 29 transmits this movement to the trigger lever 14 which acts upon the pawl 11 of the sear 8 thereby etfecting release of the breech block. During rotation of the intermediate lever 17 the movable stop 26 is first pressed backwards by the face 29 of the pawl 20 (Fig. 7) but returns to its initial position under the action of the spring 27 as soon as the face 29 of the pawl 20 has slid off the face 30 of the stop 26. The face 31 of the pawl 20 is now immediately above the face 32 of the stop 26 (Fig. 8). When the trigger is released (Fig. 9). The latter is immediately turned by the spring 34, releasing the pawl 11 of the sear 8 whereupon the breech block 4 is caught. If the trigger is not released until the last round has been removed from the magazine the rocking lever 40 is actuated by the spring-operated releaser 44 and releases the plunger 36. The latter,

under .the action of. the spring 38, rotates the lever 37.'

Since the lever 37 is connected to the pawl 20 via the coupling claws 24, engaging faces 25 of the pawl 20, the latter is brought out of engagement with the trigger lever 14, whereupon the pawl 11 returns the sear 8, to locking position.

Figs. l0l2 show another constructional example of the present invention. Therein the intermediatelever 49 actuated by the trigger 48 carries the pawl 50 which engages directly withthe sear 51. The pawl 50 is acted upon by the lever 53 which rotates about the pin 52 and is subjected to the pressure of spring 54. The operation of this constructional example as shown in the three figures is substantially similar to the operation of the first example previously described in detail.

These constructional examples of the present invention described here are, of course, only two out of numerous possible designs.

We claim:

1. In a trigger and sear mechanism for automatic firearms, in combination with a movable breech block having an abutment, a spring-engaged pivoted sear having a face engaging said breech block abutment in a locking position to lock said breech block, a pivoted triggeractuated, spring-engaged intermediate lever, a catch pivoted upon said intermediate lever, said sear having a scar abutment adapted to be engaged by said catch, and a arms, in combination with a movable breech block having an abutment; a pivoted sear having a face engaging said breech block abutment in a locking position of the sear to lock said breech block, a catch pivoted upon said sear and engaging said breech block in a locking position of the catch to maintain said sear in its locking position, resilient means between said catch and said sear, a spring engaging said sear, said spring moving said sear to an unlocked position in which said breech block is released said catch is disengaged from said breech block and a PIVOtCd' trigger lever adapted to engage said catch, said lever moving said pawl from the locking position to a the pawl 20 is rotated by the stop 26 and, when the inter- I disengaged position; a pivoted trigger-actuated, springengaged intermediate lever, a latch pivoted'upon said intermediate lever, said trigger lever having a nose adapted to be engaged by said latch, a spring connected with said latch and pressing it into engagement with the nose of said trigger lever, and a spring-engaged stop adapted to engage said latch and to disengage it from said trigger lever upon release of said intermediate lever, whereby said catch is immediately moved to its locking position.

3. In a trigger and sear mechanism for automatic firearms, in combination with a breech casing, a breech block movable in said casing and having an abutment; a pivoted sear having a face engaging said abutment in a locking position of the sear to lock said breech block, catch pivoted upon said scar and engaging said breech block in a locking position of the catch to maintain said sear in its locking position, resilient means between said catch and said sear, a spring engaging said sear, said spring moving said sear to an unlocked position in which said breech block is released when said catch is disengaged from said breech block, and a pivoted trigger lever adapted to engage said catch, said lever moving said catch from the locking position to a disengaged position; a pivoted trigger-actuated, spring-engaged intermediate lever, a latch pivoted upon said intermediate lever, said trigger lever having a nose adapted to be engaged by said latch, a

spring connected with said latch and pressing it into enment with the nose of said trigger lever, a stop mount- -.t. .11 said breech casing, a spring engaging said stop, said stop bein adapted to engage said latch and to disengage it from said trigger lever upon release of said intermediate lever, whereby said catch is immediately moved to its locking position.

4. In an automatic firearm, a sear mechanism having a swinga'ole catch; a trigger-operated lever swingable from a rest position to an operative position and vice versa, means operatively connecting said lever with said sear mechanism during the swinging of said lever from said rest position to said operative position, said means comprising a latch pivoted upon said lever; and a stop for said latch, said stop engaging said latch at the begin ning of the movement of said lever from said operative position to said rest position to interrupt the operative connection between the lever and the sear mechanism.

5. In an automatic firearm having a movable breech block a scar mechanism having a catch swingable into a locking position, said catch locking said breech block in said locking position, a trigger-operated lever swingable from a rest position to an operative position and vice versa, a latch pivoted upon said lever, resilient means engaging said latch and maintaining said latch during the swinging of said lever from said rest position to said operative position in engagement with said sear mechanism to provide operative connection between said lever and said sear mechanism; a movable member, resilient means pressing said member into the path of movement of said latch during the swinging of said lever, said latch moving said member out of said path of movement during the swinging of said lever from said rest position into said operative position, and said member turning said latch against the action of the first-mentioned resilient means at the beginning of the movement of said lever from said operative position into said rest position to interrupt said operative connection.

References Cit-ed in the file of this patent UNITED STATES PATENTS 

